Prefabricating modular building units constructed from standardized components in a controlled factory setting can be desirable due to the lowered costs and the increased quality which is obtainable in comparison to performing similar work on an outdoor construction job site.
Thus prefabricated modular building units having a floor, walls and an overhead structure, and which contain all the systems and furnishings pre-installed within them are preferred and well known in the art. Building assembly systems composed of the means and methods to join two or more modular building units together to form a larger structure are also well known in the art.
Devices which engage a specially prepared aperture on the upper or side surface of the structural frame so as to provide a releasable connection for the purpose of lifting and moving the modular building units are well known in the art.
A limitation to the construction of slender or tall buildings using factory-built modules is the inability of economically constructed modules to resist and transmit the large moments and tension forces resulting from wind and seismic forces and the large compression loads resulting from the effect of gravity on the building and occupants. Further, all of these force types are exaggerated by narrowness in one or both axes of the building. These effects are greatest in the lower floors and rise in proportion to increasing height and slenderness, so forces are also largest at the lower floors. It is a characteristic of many modular construction systems that the pinned nature of the connections between adjacent modules and the lack of diagonal bracing beyond that necessary for integrity in shipping can limit the effectiveness of force transmission through a larger assembly of conventional module types.
The state of the art for constructing tall or slender building using modules as taught in the art cited herein is to maintain the economies of scale in production by either reinforcing the entirety of all modules of which the building is composed, so all contribute to resisting the forces in a distributed fashion as a stack of ocean freight containers do; or to employ large columns which are situated within or outside of the walls of all of the modules, creating an alternate load path; or to construct an adjoining or interconnected brace frame which by-passes the modules and transmits the large loads to the ground through the secondary structure; or to make use of a tension rod or cable which passes vertically through the building to anchor the modules against uplift and lateral drift. All of the above noted approaches can have limitations in the achievable resistance to forces and transmission of forces, or require the erection of an additional structure, which in turn can limit the achievable height or increases the amount of material used, therefore increasing the cost.
Additionally, methods of construction which employ large columns, particularly when grouped at corners or where occurring at intermediate locations within the walls result in larger spaces between modules, and/or walls of increased thickness which reduces the useful floor area of the resulting building, and/or projections which limit the free use of the voids and walls for the purposes of installing fixtures such as cabinets and shower stalls, and/or which imposes other limitations on the use of the space by the inhabitants, thereby decreasing the value of the resultant building.
Additionally, methods of modular building construction which employ secondary frames add to the assembly time for the building, increasing the cost and duration of construction and reducing the useful floor area, thereby decreasing the value of the resultant building.
Creating a multiplicity of dissimilar module types each having unique details relative to the forces acting on the module within a building is undesirable, as increased variation increases the number of unique components which must be measured, cut and inventoried until use. Additionally, setups of the manufacturing tooling required to accurately locate these parts relative to each other for assembly is error-prone and therefor normally executed by skilled persons, so any increase in the number of setups adds to both production time and cost.
Because the members comprising a networked structure must be of nearly identical length, creating the numerous features required to accurately assemble modules by welding or other means, the subsequent location and connection of the subassemblies of which a module is made, the rigging and hoisting of the completed modules and the fastening of the modules to form structurally sound groupings which provide redundant and adequate load paths as currently practiced, requires a number of precision cutting and assembly operations which increase cost.
It is well known in the art that a moment-connected module frame or building frame reduces the need for diagonal reinforcing elements which otherwise obstruct the view of the occupants and hinder the installation and maintenance of building services. However moment connections which require expansive splice plates as a means of connection require clear access to one or more faces of the module, thus increasing the amount of enclosing and finishing work which must be completed at the site.
Some embodiments of a modular building which best suit the site conditions, the needs of the occupants and the aesthetic tastes of the architect or owner may be composed of module forms having non-orthogonal shapes, including tapering, curving, polygonal etc. however existing systems for the construction of structural modules suited to tall building construction are by nature not suited to non-orthogonal shapes.
Varying shapes of modules and the varying location of walls, fixtures and other components causes the centre of gravity of modules used to construct a building or to furnish a single floor of said building, to vary. To facilitate placement while reducing the clearances to a minimum it is desirable to have the side walls of the modules oriented as closely to perpendicular as possible during hoisting. It has been the case that lengthy delays and repeated trial lifts are required to effect adjustments of the rigging so as to achieve this desirable condition. The time required to make the required changes in turn increases the total duration of the hoisting operation, thus increasing costs for both labour and equipment such as cranes as well as delaying the completion of the building.
The requirement to place and inter-connect modules which are not accurate increases the amount of space required between modules, which increases the difficulty of fireproofing the structure and the difficulty of interconnecting the members so as to achieve the greatest possible strength as well as making integration of modules in to structural groups more difficult and wasting space and providing space for the circulation of sound, smoke and vermin.
The dimensions of a module and the positional disposition of the members within it defines the position and size of the outer wall facings, of the mechanical services, of the abutting and adjoining modules and of the support structures beneath the building and a such there is an interdependent relationship between all the elements of which a modular building is composed.